/Engine/Source/Developer/PakFileUtilities/Public/PakFileUtilities.h
Defines the order mapping for files within a pak. When read from the files present in the pak, Indexes will be [0,NumFiles). This is important for detecting gaps in the order between adjacent files in a patch .pak. For new files being added into the pak, the values can be arbitrary, and will be usable only for relative order in an output list. Due to the arbitrary values for new files, theFPakOrderMapcan contain files with duplicate Order values.
class FPakOrderMap